Basic Medic strategy
The Medic is the designated healer of Team Fortress 2 Classic. His Mediguns allow him to sustain his team and buff them to up to 150% of their health as temporary Overheal, building up Übercharge as he does, gaining more Über from healing injured teammates. The Shock therapy also allows for periodic bursts of huge healing at the cost of the heal speed of his secondaries. Each medigun has a unique Über effect, i.e. invulnerability and 100% critical chance, which can easily turn the tides of any battle if used effectively, making the Medic a high-priority target for the enemy team. The Medic is mostly defenseless, save for his teammates, as his weapons are ineffective in direct combat. Soldiers, Demomen, Pyros and Heavies are particularly favored as Über recipients for their potential for high damage output in a short amount of time. Snipers and Spies are usually not good Über targets, as they are often granted situational crits and are more single-target focused, Engineers for their lack of non-sentry damage output and hesitance to leave their nests, Medics for their aforementioned combat ineptitude, and Scouts for their inconsistent burst damage and tendency to outrun the Medic. It is, however, important to heal the Civilian, as his life is extremely important, but the Kritzkrieg Über should never be used on him.
Primary Weapons
The Syringe Gun is the Medic's only primary weapon and has a weak damage output with slow-moving, gravity-affected, inaccurate projectiles. At medium range, it deals 7-10 damage per needle, and fires 9.5 times per second. It also has a small clip size, emptying in just above 4 seconds of continuous fire, and has a painfully long reload time. This weapon is generally useless in direct combat, and should only be used while retreating after your patient dies with no teammates around, and only until you find another teammate. It really shines while retreating, as enemies will tend to run into your shots as you make use of the Medic's high base speed to escape. It's advisable to use any downtime to make sure to reload your Syringe Gun to not get caught off guard if your patient were to suddenly die. Its projectiles could be used offensively in a similar fashion to the Nailgun.
Secondaries
Despite being the Medic's secondary weapons, these are certainly the weapons the Medic should be wielding the majority of the time. With a heal rate of 24-72, a minimum Übercharge build speed of 40 seconds and an Übercharge that grants Invulnerability to all damage for 8 seconds to you and your patient is certainly something to behold. This Medigun's Über is most effectively used offensively to break enemy defenses and sentry nests, negating all damage as you do so. It's best to wait until your target is at at least half health before deploying the Über, just to make the most out of the charge. The Civilian's Umbrella increases the Medi Gun's heal rate and Übercharge build rate by 35%, making the heal rate 32-97 HP/s, and the Übercharge increases by 3.3% per second on injured teammates instead of 2.5%, meaning it would fill by 27% over the 8 seconds the buff lasts for. The Medi Gun has the slowest Übercharge build rate, so it would benefit from the Übercharge-supporting effects of the Überspritze, with the invulnerability negating its health penalty.
The Kritzkrieg is an alternative to the Medi Gun which boasts an identical heal rate and overheal, but with a 25% increased Übercharge rate, meaning it fully charges in a minimum of 30 seconds as opposed to 40, and grants 100% critical chance instead of invulnerability, also for 8 seconds. This medigun is effective both offensively and defensively, to melt any enemies that may get in the charged patient's way. It is ineffective against Engineer's buildings and Übercharged enemy players due to their crit and damage invulnerability, respectively. The Civilian's Umbrella buff increases the Kritzkrieg's Heal rate the same as the Medi Gun's, and its Übercharge rate increases from 3% per second to 4.2% per second, granting 34% over the 8 seconds the buff lasts for.
The Rejuvenator trades the consistent single-target heals for a more burst and group-focused approach. The Rejuvenator does not use the beams of it's predecessors, but uses grenade-like projectiles that heal instead of harm, although that may not be as rewarding. This allows for multiple targets to be hit at once, and rewards skilled medics with longer range healing, and bonus health and Übercharge gains on a direct hit. However, the Rejuvenator's projectile-based nature comes with a few downsides. The weapon needs to reload, but it does have an unlimited ammo pool. This introduces downtime that the other mediguns just don't have. The other mediguns also automatically lock onto your patient and apply a steady stream of health straight to them. Now, you need to aim and hit them, which can prove to be difficult. The Civilian's Derby Cane's Haste boost is able to buff the Rejuvenator, unlike the other secondaries, as it increases its firing speed and reload speed. The Rejuvenator's Übercharge effect is similarly group-focused, with it deploying a device that projects a large invulnerability bubble. This is most effective on defence or gamemodes where teammates tend to be grouped up, like Control Points, VIP and Payload.
Melee Weapons
The Bonesaw is the stock melee for Medic, and deals more damage than your Syringe Gun at close range. Due to how melee crit chance is calculated, healing teammates also increases crit chance, leading Medics to have a well-earned, high crit chance where otherwise defenseless. However, its combat effectiveness is overshadowed by his other melees, which offer more utility but impact either your survivability or heal rate.
The Überspritze is an alternative to the bonesaw that trades survivability for possible Übercharge boosts. When you hit an enemy with the Überspritze, you gain 25% Übercharge, unless that enemy is invulnerable or a disguised spy. This comes at a cost of 10 maximum health, reducing the Medic's health pool to 140. This means it pairs best with the Medi Gun, as it has the slowest Übercharge build rate, and also grants invulnerability, making the lower health unimpactful. The 25% Übercharge increase may make it tempting to pursue enemies in one-on-one combat, but this should still generally be avoided, especially considering the lower health. This is also the only medic weapon with a taunt kill, and a very rewarding one at that. Other than simply killing the victim, the Medic also gains 100% Übercharge on a successful taunt kill, making it a risky but rewarding maneuver.
The Shock Therapy's CHARGE mechanic makes it both a burst healing and damage weapon, while sacrificing both usual healing and damage per second. Its CHARGE meter fills up in 30 seconds, and when full, hitting a teammate heals them for their maximum health, which can overheal. For example, hitting a Heavy on 123 HP would heal him up to 423 HP, with anything over his 300 max hp being overheal. The Shock Therapy's melee damage also scales directly with its CHARGE, Dealing 100 damage when full. This means that any Heavies using the Chekhov's Punch, could be one-shot, even at full health. Sadly, it cannot randomly crit, but it does have a much higher range than normal, being 70% longer than stock, giving you an edge over enemies in melee combat. Having this weapon equipped reduces your healing rate by 15% to 20-61 HP/s, or 28-83 HP/s with the Umbrella's buff. This also increases your Übercharge building capability, as it increases at the same speed, and you will spend more time healing injured teammates.